A retaining device for a stand includes a base, a shaft inserted in the base, a handle pivotally mounted on the shaft, and a retainer sleeved on a cam portion of the handle. When the handle is pivotally moved downwards, the retainer can be driven to move toward an extending rod of the stand by actuation of the cam portion of the handle for stopping against the extending rod of the stand and retaining the extending rod of the stand in position.